Total fatty acid composition in the characterization and identification of orchid mycorrhizal fungi Epulorhiza spp.

Rhizoctonia-like fungi are the main mycorrhizal fungi in orchid roots. Morphological characterization and analysis of conserved sequences of genomic DNA are frequently employed in the identification and study of fungi diversity. However, phytopathogenic Rhizoctonia-like fungi have been reliably and accurately characterized and identified through the examination of the fatty acid composition. To evaluate the efficacy of fatty acid composition in characterizing and identifying Rhizoctonia-like mycorrhizal fungi in orchids, three Epulorhiza spp. mycorrhizal fungi from Epidendrum secundum, two unidentified fungi isolated from Epidendrum denticulatum, and a phytopathogenic fungus, Ceratorhiza sp. AGC, were grouped based on the profile of their fatty acids, which was assessed by the Euclidian and Mahalanobis distances and the UPGMA method. Dendrograms distinguished the phytopathogenical isolate of Ceratorhiza sp. AGC from the mycorrhizal fungi studied. The symbionts of E. secundum were grouped into two clades, one containing Epulorhiza sp.1 isolates and the other the Epulorhiza sp.2 isolate. The similarity between the symbionts of E. denticulatum and Epulorhiza spp. fungi suggests that symbionts found in E. denticulatum may be identified as Epulorhiza. These results were corroborated by the analysis of the rDNA ITS region. The dendrogram constructed based on the Mahalanobis distance differentiated the clades most clearly. Fatty acid composition analysis proved to be a useful tool for characterizing and identifying Rhizoctonia-like mycorrhizal fungi

Characterization of selected strains of mucorales using fatty acid profiles Caracterização de linhagens de mucorales através do perfil de ácidos graxos

The fatty acid profiles of several fungi of the order Mucorales (Zygomycetes), including Backusella lamprospora (Lendner) Benny and R.K. Benj., Benjaminiella youngii P.M. Kirk, Circinella simplex van Tieghem, Cunninghamella blakesleeana Lendner, Mortierella ramanniana (Möller) Linnem., Mucor circinelloides f. janssenii (Lendner) Schipper, Mycotypha microspora Fenner, Rhizomucor miehei (Cooney and R. Emerson) Schipper and Rhizomucor pusillus (Lindt) Schipper, and of Volutella sp. Fr., from the class Ascomycetes, were qualitatively analysed by gas-liquid chromatography in order to determine the taxonomic value of these chemotaxonomic markers. The fatty acids present in all strains were palmitic (16:0), oleic (18:1), linoleic (18:2) and <FONT FACE="Symbol">g</FONT>-linolenic (18:3) acid, with the exception that the latter was not found in Volutella sp. Chemotaxonomic markers for some species and genera were obtained, including a non-identified fatty acid, FAME8 (minimum and maximum retention times of 27.92 and 28.28 minutes) for Rhizomucor miehei CCT 2236 and Rhizomucor pusillus CCT 4133, and FAME3 (minimum and maximum of 16.53 and 16.61 minutes) for Benjaminiella youngii CCT 4121. The chemotaxonomic marker of the order Mucorales was the fatty acid 18:3<FONT FACE="Symbol">w</FONT>6, confirming previous data from literature. The results of the present study suggest that qualitative fatty acid analysis can be an important chemotaxonomic tool for the classification of fungi assigned to the order Mucorales (Zygomycetes).<br>O perfil de ácidos graxos de Backusella lamprospora (Lendner) Benny e R.K. Benj., Benjaminiella youngii P.M. Kirk, Circinella simplex van Tieghem, Cunninghamella blakesleeana Lendner, Mortierella ramanniana (Möller) Linnem., Mucor circinelloides f. janssenii (Lendner) Schipper, Mycotypha microspora Fenner, Rhizomucor miehei (Cooney e R. Emerson) Schipper e Rhizomucor pusillus (Lindt) Schipper, da ordem Mucorales (Zygomycetes), e Volutella sp. Fr., da classe Ascomycetes, foram analisados qualitativamente por cromatografia gás-líquida, tendo como objetivo determinar o valor taxonômico destes marcadores quimiotaxonômicos. Os ácidos palmítico (16:0), oléico (18:1), linoléico (18:2) e <FONT FACE="Symbol">g</FONT>-linolênico (18:3) foram encontrados em todas as linhagens, com exceção do último, o qual não foi encontrado na linhagem de Volutella analisada. Foram obtidos marcadores quimiotaxonômicos para algumas espécies e gêneros estudados, incluindo um ácido graxo não-identificado, FAME8 (tempos de retenção mínimo e máximo de 27,92 e 28,28 minutos) para Rhizomucor miehei CCT 2236 e Rhizomucor pusillus CCT 4133 e FAME3 (tempos de retenção mínimo e máximo de 16,53 e 16,61 minutos) para Benjaminiella youngii CCT 4121. Para a ordem Mucorales, o marcador quimiotaxonômico obtido foi o ácido graxo 18:3<FONT FACE="Symbol">w</FONT>6, confirmando dados da literatura. Os resultados do presente estudo sugerem que a análise qualitativa do perfil de ácidos graxos pode ser uma ferramenta importante na classificação de fungos da ordem Mucorales (Zygomycetes)